Field
The disclosed and claimed concept relates generally to electronic devices and, more particularly, to a magnetic linear actuator.
Related Art
Electromagnetic actuators are devices commonly found in power equipment and provide working motion via of an internal electromagnetic field, with the motion of the actuator providing a control or switching function in such power equipment. Electromagnetic actuators provide the movement used for actuation by exposing a free moving plunger or armature to the magnetic field created by energizing a static wire coil. The field attracts the plunger or armature which resultantly moves with respect to the field, thus providing the required actuation. Varying degrees of actuation functionality can be achieved with an electromagnetic actuator, ranging from simple single-cycle, single-speed actions to fairly sophisticated control of both actuation time and positioning.
One type of commonly used electromagnetic actuator is a permanent magnet actuator, which makes use of one or more permanent magnets and electric energy to control positioning of a plunger therein. Permanent magnet actuators may be configured such that the plunger thereof is held at a stroke position due to the permanent magnet, with electricity being applied to the wire coil to move the plunger to a different stroke position.
In such permanent magnet actuators, the wire coil typically is employed to move the armature to a first position in proximity to the permanent magnet and to overcome the bias of a return spring that biases the armature in a direction generally away from the permanent magnet. When it is desired to move the armature away from the permanent magnet to move the armature to a second position spaced from the first position, the wire coil typically is energized with a reverse polarity so that its magnetic field counteracts that of the permanent magnet, which resultantly permits the bias of the return spring to overcome the partially counteracted magnet attraction of the permanent magnet. It is noted, however, that the energy that is used to power the wire coil in order to move the armature away from the permanent magnet is typically stored in large capacitors, and the charge necessary to energize the wire coil sometimes can be absent if the charge therein has been dissipated due to non -use of the actuator for an extended period of time. In such an event, significant forces are typically required to be applied to the armature in order to overcome the magnetic attraction of the permanent magnet. Such forces can be difficult to apply, and the need to apply them is undesirable in a situation where a rapid movement of the armature away from the permanent magnet is needed, such as in order to switch a circuit breaker from an ON position to an OFF position in a hurry. Improvements thus would be desirable.